Opposite rotational sense actuator mechanism for tap changer contacts



April 12, 1966 J. A. MAUNDER 3,246,088

OPPOSITE ROTATIONAL SENSE ACTUATOR MECHANISM FOR TAP CHANGER CONTACTS Filed Oct. 14, 196-3 2 Sheets-Sheet l '//////A;// TI7//// '""131E511".......

ldvnv'rolL JEFFREY ALLEN Mfi'U/VDEK B =MM+ W n1 April 12, 1966 MAUNDER 3,246,088

OPPOSITE ROTATIONAL SENSE ACTUATOR MECHANISM FOR TAP CHANGER CONTACTS Filed 00 14, 1963 2 Sheets-Sheet 2 United States Patent OPPOSITE ROTATIONAL SENSE ACTUATOR MECHANISM FOR TAP CHANGER CONTACTS Jelfrey Allen Maunder, Manchester, England, assignor to Associated Electrical Industries Limited, London, Eng- 3 land, a company of Great Britain Filed Oct. 14, 1963, Ser. No. 316,077 Claims priority, application Great Britain, Oct. 19, 1962, 39,699/ 62 Claims. (Cl. 200-11) This invention relates to selector switches suitable for use for transformer on-load tap changing.

A known arrangement for transformer on-load tap changing employs two selector switches each comprising a plurality of fixed contacts, usually arranged on a circle and a movable contact operable to engage the fixed contacts in sequence. One of these two selector switches has its fixed contacts connected to odd-numbered tapping points on the transformer and the other has its fixed contacts connected to even-numbered tapping points, a high speed diverter switch being provided to direct the load current through one or the other of the selector switches depending on whether an odd-numbered or an evennumbered tapping point is in use. The two selector switches are arranged to be operated, alternately, to move the movable contact from one fixed contact to the next in the sequence, so that the tapping point in use can be progressively changed, with minimum disturbance of the load circuit, by operating the selector switch not in use and then operating the diverter switch to connect this selector switch to the load and disconnect the other selector switch. With the fixed contacts of the selector switches arranged on circles, the two selector switches are usually mounted, one above the other, on two concentric shafts, respectively coupled to the movable contacts of the two selector switches, the two shafts being arranged to be rotated alternately to operate the movable contacts each through one step at a time.

It is a disadvantage of this known tap changing arrangement that the two fixed contacts which are first and last in the circular sequence of engagement by the moving contact of a switch are connected to tapping points having most of the tapped voltage between them. Consequently these two fixed contacts, which are next to each other in the circle of contacts, must be spaced apart sutficiently to withstand this voltage and any voltage surges which may occur.

It is an object of the invention to provide a selector switch which can replace both of the selector switches of the known arrangement and also does not suffer from the above disadvantage.

According to the invention a selector switch suitable for on-load transformer tap changing comprises a plurality of fixed contacts arranged in two arcuate sets, preferably on a common circle, and two contra-rotatable movable contacts operable to selectively engage the fixed contacts of the respective sets, the two movable contacts being arranged to be stepped alternately, each from one fixed contact to the next, between limit positions in one of which they respectively engage the fixed contacts at adjacent ends of the respective arcs and in the other of which they respectively engage the fixed contacts at the other end of these arcs.

By reason of this arrangement, if the fixed contacts of one set are successively connected to the odd-numbered tapping points, and those in the other set to even-numbered tapping points, the end fixed contacts of the two arcs, at each end, will be connected to adjacent tapping points and will consequently have to be spaced only to withstand the voltage between these tapping points.

In order that the invention may be more fully understood an embodiment thereof will now be described, by way of example, with reference to the accompanying drawings in which:

FIG. 1 represents in plan view a selector switch in accordance with the invention;

FIG. 2 is a section taken along the line AA in FIG. 1;

FIG. 3 is a transformer on-load tap changing arrange ment which includes a selector switch in accordance with the invention; and

FIG. 4 is a similar section to FIG. 2 but shows in addition a driving mechanism for the switch.

Referring in the first instance to FIGS. 1 and 2, an insulating plate 20 carries a plurality of fixed contacts '1, 2, 3, 4 11 arranged on a circle surrounding two arcuate collector bars 21 and 22 which are also carried by the plate 20. The fixed contacts designated by the odd numerals 1, 3, 5 etc. form an arcuate, substantially semicircular, set associated with collector bar 21 and selectively connectible thereto by movable contact 23 carried by an arm 24 radially disposed with respect to the fixed contact circle. Another radial arm 25 carries a movable contact 26 arranged to selectively connect to the collector bar 22 the arcuate, substantially semi-circular, set of fixed contacts formed by those designated by the even numerals 2, 4, 6 etc. The plate 20 may conveniently be moulded from a suitable synthetic resin which can withstand high voltages and may have the fixed contacts 1, 2 11 and the collector bars 21 and 22 moulded therein. The arms 24 and 25 are contra-rotatable by concentric shafts 27 and 28 which are coupled to a suitable driving mechanism (such for instance as that shown in FIG. 4) arranged to step the arms 24 and 25 alternately and in opposite directions round the circle to engage the fixed contacts of their associated sets in sequence. Starting with the arms 24 and 25 in the positions shown, that is, with movable contacts 26 and 23 engaging fixed contacts 4 and 5 respectively the shaft 28 can be rotated to step the arm 25 to a position in which its contact 26 engages fixed contact 6, then shaft 27 can be rotated to step the arm 24 to a position in which its contact 23 engages fixed contact 7, and so on. The two shafts 27 and 28 can be rotated alternately in this manner until the arms 24 and 25 have been stepped to the limit position in which their contacts 23 and 26 engage fixed contacts 11 and 10 respectively. Alternate rotation of the two shafts 27 and 28 in the reverse direction can be effected until the arms 24 and 25 reach the limit positions in which their contacts engage the fixed contacts 1 and 2.

In the form of driving mechanism shown in FIG. 4, a shaft 30- is rotatably mounted on one end of shaft 27 of the switch and intermittently transmits rotary motion to it through a 2:1 reduction gear train 31, 32, and a Geneva mechanism comprising a star wheel sector 33 and a cam 34. The shaft 30 also intermittently transmits rotary motion to the shaft 28 through a 2:1 reduction gear train 36, 37 with an interposed direction reversing idle wheel 38, and a Geneva mechanism comprising star wheel sector 39 and a cam 40. A bevel gear 41, 42 couples a driving shaft 43 to the shaft 30. In operation, the driving shaft 43 rotates the shaft 30, causing the gear wheels 32 and 37 to rotate in opposite directions. The cams 34 and 40 are driven by the latter gear wheels and are so phased (that is, they have such angular positions relatively to each other) that they engage a tooth of their respective star wheels sectors 33 and 39 alternately, so that these sectors and with them the shafts 27 and 28 move in opposite directions through a limited angle, alternately. With gear trains having a 2:1 reduction ratio as mentioned each complete revolution of the shaft moves one of the shafts 27 and 28 through a small angle so that its associated movable contact steps from one fixed contact to the next in the sequence.

Referring now to FIG. 3, a transformer winding W has a plurality of tapping. points t t t connected to the two sets of fixed contacts of a selector switch in accordance with the invention as shown. The collector bars 21 and 22 of the switch are connected to contacts of a high speed diverter switch Dv arrangedto selectively con.- nect the collector bars to a load terminal L. When connected in this manner the, voltage between any two adjacent fixed contacts is. only that between two consecutive tapping points. With tapping points t in use, the arms 24 and 25 being in the positions illustrated in FIG. 1, a change to tapping point t is. eifected by operating the selector switch to the position in which contact 26 engages fixed contact 6 and then operating the'diverter switch D to connector bar 22 to the load terminals L. A subsequent change to tapping point t can. be effected by operating the selector switch. so that contact 23 engages fixed contact 7 and then returning the diverter switch to its original position to connect bar 21 to the load terminal L. y The plate 20, which as shown can be circular so as to simplify the construction of its mould, can be suitably dished to provide strength. The, circular form for the plate 26 is also advantageous for single-phase high voltage taps changers in that the plate can be mounted concentrically at the bottom of the porcelain insulator on the top of which the diverter switch is usually mounted. The fixed contacts, which all lie in the same plane are readily accessible. and enable connections to the tappingv points to be etfected easily.

What I claim is:

1. A selector switch comprising a support structure, a plurality of electrically isolated fixed contacts arranged on the support structure in two arcuate sets having their arcs centered on a common axis and subtending respective angles each of less than. 180 degrees on opposite. sides of said axis, first and second movable contacts cooperating respectively with said two sets of fixed contacts and.

mounted on said support structure for rotation about said axis, each over the fixed contacts of the appertaining set, actuating means coupled to the movable contacts for stepping them alternately and in opposite rotational sensesof the respective arcuate sets, and connection'means for establishing continuous electrical connection with said movable contacts throughout their movement between said limit positions.

2. A- selector switch as claimed in claim 1, in which the two sets of fixed: contacts are arranged on said: support structure at a common radialdistance from said axis and in the same; plane.

3. A selector switch as. claimed in claim 1 including two concentric shafts respectively carrying s'aid movable contacts, a common rotatable operating member, and means drivingly coupling said concentric shafts to said common member; said means'inc'luding direction reversing gearing in respect of one of said shafts, and respective intermittent drive mechanismsfor both said shafts, said mechanisms being phased to act alternately whereby to step said shafts and therefore-the movable contacts alternately'and in opposite rotational senses.

4. A selector switch as claimed in claim 1 in electrical combination with a. tapped transformer having successive odd and even numbered tapping points, said transformer having connections. electrically connecting-its successive odd-numbered tapping points to the successive contacts in one of said sets of' fixed contacts of. the switch, and con-- References Cited by the Examiner UNITED STATES PATENTS 1,764,319 6/1930 Kurda 323-435 1,863,392 6/1932 Brand etal 200-7 1,867,147 7/1932 Haller 2004 2,231,627 2/1941 Jansen.

2,363,886 11/1944 McKenney' 200-5 2,480,589 8/1949 McKenney 32343.5 2,560,002 7/ 1 SeaIey.

2,785,242 3/1957 White 200-18 3,155,782 11/1964 Wilson u 200'-11 KATHLEEN H. CLAFFY, Primary Examiner- 

1. A SELECTOR SWITCH COMPRISING A SUPPORT STRUCTURE, A PLURALITY OF ELECTRICALLY ISOLATED FIXED CONTACTS ARRANGED ON THE SUPPORT STRUCTURE IN TWO ARCUATE SETS HAVING THEIR ARCS CENTERED ON A COMMON AXIS AND SUBTENDING RESPECTIVE ANGLES EACH OF LESS THAN 180 DEGREES ON OPPOSITE SIDES OF SAID AXIS, FIRT AND SECOND MOVABLE CONTACTS COOPERATING RESPECTIVELY WITH SAID TWO SETS OF FIXED CONTACTS AND MOUNTED ON SAID SUPPORT STRUCTURE FOR ROTATION ABOUT SAID AXIS, EACH OVER THE FIXED CONTACTS OF THE APPERTAINING SET, ACTUATING MEANS COUPLED TO THE MOVABLE CONTACTS FOR STEPPING THEM ALTERNATELY AND IN OPPOSITE ROTATIONAL SENSES BETWEEN LIMIT POSITIONS IN ONE OF WHICH THE FIRST MOVABLE CONTACT ENGAGES THE FIXED CONTACT AT ONE END OF THE APPERTAINING ARCUATE SET WHILE THE SECOND MOVABLE CONTACT ENGAGES THE FIXED CONTACT AT THE NEAR END OF THE OTHER ARCUATE SET, AND IN THE OTHER OF WHICH THE MOVABLE CONTACTS RESPECTIVELY ENGAGE THE FIXED CONTACTS AT THE OTHER ENDS OF THE RESPECTIVE ARCUATE SETS, AND CONNECTION MEANS FOR ESTABLISHING CONTINUOUS ELECTRICAL CONNECTION WITH SAID MOVABLE CONTACTS THROUGHOUT THEIR MOVEMENT BETWEEN SAID LIMIT POSITIONS. 